The present invention relates to an automatic transmission and a range shift device.
In general, a running range of a vehicle provided with an automatic transmission is set by a driver operating a shift lever that moves a manual valve and thus changes oil passage. A system known as a shift-by-wire system can be used for setting the running range selected by the driver through an electric signal, without relying on a mechanical wire or rod (see Japanese Patent Application Publication No. JP-A-2005-207570 for an example).
Furthermore, a range shift device for shifting the running range can also be used as described in Japanese Patent Application Publication No. JP-A-2005-207570, for example. FIGS. 10A-10C show such a range shift device 201. The vehicular range shift device 201 includes a motor 204 for rotational driving based on an electric signal from a shift lever (not shown), which acts as manually operated shift operating driver; a mechanical transmission mechanism 260 for transmitting the rotation of the motor 204 to a manual valve (not shown); and a detent member (not shown). The mechanical transmission mechanism 260 includes a ball screw shaft 221, a ball nut 222, and an arm member 206. The rotational motion that has been output from the motor 204 is designed to convert back to a rotational motion following a conversion from rotational motion to linear motion. Also, the motor 204 is provided on an outer side of a housing 210 of the range shift device 201, and the mechanical transmission mechanism 260 is accommodated in the housing 210.
In addition, the range shift device 201 is provided in a case 262 of an automatic transmission. Inside the case 262, a speed change mechanism is provided for changing a speed of an engine, and a lubricant (i.e., oil) circulates.
Based on the electric signal generated by a manual operation of the shift lever, the range shift device 201 operates the manual valve (not shown), via the mechanical transmission mechanism 260 and the detent member, so as to shift the engine speed range in the automatic transmission.